What is the etiology of tuberculosis (TB)?

Updated: Jun 04, 2020
  • Author: Thomas E Herchline, MD; Chief Editor: Michael Stuart Bronze, MD  more...
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TB is caused by M tuberculosis, a slow-growing obligate aerobe and a facultative intracellular parasite. The organism grows in parallel groups called cords (as seen in the image below). It retains many stains after decoloration with acid-alcohol, which is the basis of the acid-fast stains used for pathologic identification.

Acid-fast bacillus smear showing characteristic co Acid-fast bacillus smear showing characteristic cording in Mycobacterium tuberculosis.

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